Long lasting vaccines comprising liposomes and a variety of antigens have been previously described in the art. These vaccine compositions have been shown to be effective in inducing an enhanced humoral immune response (determined by increased antibody production) against a specific antigen, which is dependent on T helper 2 (Th2) function. However, for a composition to adversely affect cancer, it must be able to induce a cell-mediated (cytotoxic T lymphocyte (CTL)) response. A CTL is a sub-group of T lymphocytes that is capable of inducing the death of infected somatic or tumor cells; they kill (lyse) cells that are infected with viruses (or other pathogens), or are otherwise damaged or dysfunctional. A CTL response is mediated through T helper 1 (Th1) cytokines.
In general, CTL responses are short-lived, lasting only several weeks; (Knutson et al., Clin. Cancer. Res. 8(5) 1014-1018, 1990; Dudley et al., J. Immunother. 24(4):363-73, 2002; and Fernando et el., Scand. J. Immunol. 47(5):459-65, 1998). Recurrence of cancer is always of concern, thus the induction of a long-lasting CTL response is necessary to ensure that cancers do not reoccur.
Thus, there remains a need for the development of long-lasting immune-therapeutic compositions for use in the treatment of cancer, without the need for multiple booster treatments.